Pull down some changes from the DMC migration. (microsoft#252)

Trivial changes.

DocGen/Documentation/Concepts.md

@@ -1,9 +1,10 @@
 ---
 title: World Locking Tools concepts
-description: Explaining the problems World Locking Tools solves, and how it solves them.
+description: Explains the problems World Locking Tools solves, and how it solves them.
 author: fast-slow-still
 ms.author: mafinc
 ms.date: 10/06/2021
+ms.prod: mixed-reality
 ms.localizationpriority: high
 keywords: Unity, HoloLens, HoloLens 2, Augmented Reality, Mixed Reality, ARCore, ARKit, development, MRTK
 ---
@@ -12,67 +13,67 @@ keywords: Unity, HoloLens, HoloLens 2, Augmented Reality, Mixed Reality, ARCore,
 
 ## The problem
 
-In the day to day physical world, space is well described by a stationary coordinate system. A motionless object in a stationary coordinate system will continue having the same coordinates forever. A group of objects laid out in a specific configuration will maintain that configuration. Two objects moving with identical velocities will remain at a fixed offset from each other.
+In the day-to-day physical world, space is well described by a stationary coordinate system. A motionless object in a stationary coordinate system will continue having the same coordinates forever. A group of objects laid out in a specific configuration will maintain that configuration. Two objects moving with identical velocities will remain at a fixed offset from each other.
 
-These and similar laws are such an basic part of existence that when they no longer hold, intuition about the world becomes unreliable.
+These and similar laws are such a basic part of existence that when they no longer hold, intuition about the world becomes unreliable.
 
 ## Previous solutions
 
 Unity's *global coordinate space* and *spatial anchors* each address different aspects of the problems caused by sensor inaccuracies and drift.
 
-Unity's global coordinate space provides a stable frame of reference, in which holographic objects remain fixed relative to one another.  While objects in this space will behave consistently relative to each other, consistency with the physical world is not guaranteed nor generally provided. Especially when the user is moving around, inconsistencies will develop.
+Unity's global coordinate space provides a stable frame of reference in which holographic objects remain fixed relative to one another.  While objects in this space will behave consistently relative to each other, consistency with the physical world is not guaranteed nor generally provided. Inconsistencies will develop especially when the user is moving around.
 
-Unity's spatial anchors can maintain a hologram's position in the physical world when the user is mobile, but at the sacrifice of self consistency within the virtual world. Different anchors are constantly moving relative to one another. They are also moving through the global coordinate space, making simple tasks like layout difficult, and physics simulation problematic.
+Unity's spatial anchors can maintain a hologram's position in the physical world when the user is mobile, but at the sacrifice of self-consistency within the virtual world. Different anchors are constantly moving relative to one another. They are also moving through the global coordinate space, making simple tasks like layout difficult, and physics simulation problematic.
 
 ## The source of the problem
 
-Discussion here will center around HoloLens technology, but these concepts apply generally to inside out marker-less tracking techniques, especially as augmented by inertial systems.
+Discussion here will center around HoloLens technology, but these concepts apply generally to inside-out markerless tracking techniques, especially as augmented by inertial systems.
 
-The HoloLens is amazing at determining where it is relative to visible features in the surroundings. By extension, it is also amazing at positioning other virtual objects by those same visible features. So when the user is sitting or standing in a roughly constant position, the device is great at keeping virtual objects registered with visible physical reference points. A virtual cup placed on a physical table, will mostly stay in the same spot on the surface of the table.  
+The HoloLens is amazing at determining where it is relative to visible features in its surroundings. By extension, it's also amazing at positioning other virtual objects based on those same visible features. When the user is sitting or standing in a roughly constant position, the device is great at keeping virtual objects registered with visible physical reference points. A virtual cup placed on a physical table will mostly stay in the same spot on the surface of the table.  
 
 That's when the HoloLens is confined to the same small volume, with a constant set of visible features in view for reference. But there are other interesting scenarios.
 
-When the user gets up and moves about the room, or possibly even between rooms, the HoloLens must switch between old features leaving view and new features coming into view. Without getting into implementation details, it's clear to see that while in transit, tracking accuracy is going to be very much degraded.
+When the user gets up and moves about the room, or possibly even between rooms, the HoloLens must switch between old features that are leaving view and new features that are coming into view. Without getting into implementation details, it's clear to see that while in transit, tracking accuracy is going to be very much degraded.
 
 Here's a simplistic scenario for context.
 
 ### Illustration
 
-The user is at point A. Looking around, there are a number of good visible reference features, so the head tracking quality is excellent, and any holograms placed will stay put.
+The user is at point A. Looking around, there are many good visible reference features, so the head tracking quality is excellent, and any holograms placed will stay put.
 
-The user then walks 10 meters (real, in physical space) to point B. But on reaching point B, because of the lower fidelity tracking in transit, the device registers that it has traveled exactly 9 meters. This is a large even amount for illustration, but is consistent with the device specifications, that allow a +-10% distance error in such a case.
+The user then walks 10 meters in physical space to point B. But tracking in transit has lower fidelity, so as a result, after the user reaches point B, the device registers that it has traveled only 9 meters. This is a large even amount for illustration, but it's consistent with the device specifications, which allow a +-10% distance error in such a case.
 
-Now looking around at point B, good visible features are recorded. Tracking and stability of holograms at point B is excellent too.
+As the device looks around at point B, good visible features are recorded. Tracking and stability of holograms at point B is excellent, too.
 
-When at point A, things around point A look great, and when around point B, things at point B look great. But there's an inconsistency. The 10 meters between points A and B in physical space are only 9 meters in virtual space. That's often referred to as "the scale problem", although "the distance problem" might be more accurate. Regardless, we'll get back to when that's a problem soon.
+While the user is at a particular point, things around that point look great. But there's an inconsistency. The 10 meters between points A and B in physical space are only 9 meters in virtual space. That's often referred to as "the scale problem", although "the distance problem" might be more accurate. We'll look into that problem soon.
 
-But first, the user walks back to point A. This time the tracking errors make the 10 meters walk from B to A in physical space add up to 10.5 meters in virtual space. And that means that the full walk from A to B to A adds up to a net move of 1.5 meters, when it should obviously be 0.0 meters. This is an obvious problem. A hologram placed at point A before the walk will now appear 1.5 meters away from point A.
+Back to our scenario: for the next action, the user walks back to point A. This time the tracking errors make the 10-meter walk from B to A in physical space add up to 10.5 meters in virtual space. That means that the full walk from A to B to A adds up to a net distance of 1.5 meters, when it should be 0.0 meters. This is an obvious problem. A hologram placed at point A before the walk will now appear 1.5 meters away from point A.
 
-This is where spatial anchors can help. After walking to B and back, the system recognizes that it is back at point A, yet the head's Unity coordinates have changed by 1.5 meters. But if the hologram at point A has a spatial anchor attached, the spatial anchor can think "I'm at point A, the head is at point A, but my coordinates differ from the head's by 1.5 meters. I'll just change my coordinates by 1.5 meters so that we're in agreement again." And a spatial anchor at point C, a meter to the left of the user, is going through the same process. In essence, the spatial anchor constantly redefines where point A is in Unity space so that the head's coordinates are always right. And each spatial anchor does this independently for its place in the physical world.  
+This is where spatial anchors can help. After walking to B and back, the system recognizes that it's back at point A, yet the head's Unity coordinates have changed by 1.5 meters. But if the hologram at point A has a spatial anchor attached, the spatial anchor can think "I'm at point A, the head is at point A, but my coordinates differ from the head's coordinates by 1.5 meters. I'll just change my coordinates by 1.5 meters so that we're in agreement again." And a spatial anchor at point C, a meter to the left of the user, is going through the same process. In essence, the spatial anchor constantly redefines where point A is in Unity space so that the head's coordinates are always right. And each spatial anchor does this adjustment independently for its place in the physical world.  
 
 ## World Locking Tools for Unity
 
 World Locking Tools keeps an internal supply of spatial anchors it spreads as the user moves around. It analyses the coordinates of the camera and those spatial anchors every frame. It detects when all of those spatial anchors are moving over 1.5 meters to match the coordinates of the head, and says "Hmm, instead of changing the coordinates of everything in the world to compensate for the head having different coordinates than the last time it was here, I'll just fix the head's coordinates instead."
 
 That means that, rather than having to have a spatial anchor drag a hologram through Unity space so that it will remain fixed in physical space, the entire Unity world space is locked to physical space. If a hologram is motionless in Unity space, it will remain motionless relative to the physical world features around it. And just as importantly, it will remain fixed relative to the virtual features around it.
 
-Obviously it's more complicated under the hood than that. For example, remember that a problem with the spatial anchors is that they move independently, so don't always agree with each other. The underlying FrozenWorld engine arbitrates those disagreements to come up with the most perceptually correct camera correction, and does that every frame.
+Obviously it's more complicated under the hood than that. For example, remember that a problem with the spatial anchors is that they move independently, so they don't always agree with each other. The underlying FrozenWorld engine arbitrates those disagreements to come up with the most perceptually correct camera correction, and does that every frame.
 
 ## The scale problem again
 
-If the user walks from point A to point B and back to point A, the system has enough information to fix the drift that occurred in transit. It may not know where point B is (and generally doesn't know exactly where any point B is relative to point A), but it knows whether it is at point A or not. When it gets back to point A, it expects things to be pretty much as it left them. If they aren't, it can make it so.
+If the user walks from point A to point B and back to point A, the system has enough information to fix the drift that occurred in transit. It may not know where point B is (and generally doesn't know exactly where any point B is relative to point A), but it knows whether it is at point A or not. When it gets back to point A, it expects things to be pretty much as it left them. If they aren't, the system can make it so.
 
-But what about at point B? It thought the 10 meter walk was only 9 meters. And it has no way of knowing whether that 9 meters is correct, and if it isn't, how much it is off. Spatial anchors don't help here. Spatial anchors have the same problem the head tracker does, each knows where it is in the physical world (relative to visible features), but one spatial anchor doesn't know anything about another spatial anchor. Specifically, spatial anchors don't know how far apart they are.
+But what about at point B? It thought the 10-meter walk was only 9 meters. And it has no way of knowing whether that 9 meters is correct, and if it isn't, how much it's off. Spatial anchors don't help here. Spatial anchors have the same problem the head tracker does; each knows where it is in the physical world (relative to visible features), but one spatial anchor doesn't know anything about another spatial anchor. Specifically, spatial anchors don't know how far apart they are.
 
 This can be inconvenient in many forms, but it becomes a blocking issue when objects, or systems of objects, are larger in size than a meter or so. Consider a model of a room, or a building, or a set of desks, or even a car. While a spatial anchor can keep one end of the model registered with a physical world feature, by the time the other end of the model is reached, significant error might have accumulated. The other end won't be lined up correctly. And the error will be different from device to device, and possibly even between runs on the same device.
 
-And so far in this discussion, the minimum information required to fix the problem has not been introduced.
+And so far in this discussion, the minimum information required to fix the problem hasn't been introduced.
 
-World Locking Tools addresses that problem with the [Space Pins](Concepts/Advanced/SpacePins.md) API, which allows the application to supply enough information relating the physical world and holographic world to correct for the errors in distance traveled. This allows large holograms to appear aligned with the physical world all over.
+World Locking Tools addresses that problem with the [Space Pins](Concepts/Advanced/SpacePins.md) API, which allows the application to supply enough information relating to the physical world and holographic world to correct for the errors in distance traveled. This allows large holograms to appear aligned with the physical world all over.
 
 ## Next
 
-These advanced mechanisms will be covered in later sections, but it is useful to first look in detail at World Locking Tools' baseline operation. Understanding what services the baseline operation does and doesn't supply will help in determining the proper use of advanced concepts later, and whether those advanced techniques are even required for a specific application.
+These advanced mechanisms will be covered in later sections, but it's useful to first look in detail at World Locking Tools' baseline operation. Understanding what services the baseline operation does and doesn't supply will help you to determine the proper use of advanced concepts later, and whether those advanced techniques are even required for a specific application.
 
 ## See also
 

DocGen/Documentation/HowTos/Samples/WorldLockedPhysicsSample.md

@@ -4,6 +4,7 @@ description: The most basic and general sample of World Locking Tools capabiliti
 author: fast-slow-still
 ms.author: mafinc
 ms.date: 10/06/2021
+ms.prod: mixed-reality
 ms.localizationpriority: high
 keywords: Unity, HoloLens, HoloLens 2, Augmented Reality, Mixed Reality, ARCore, ARKit, development, MRTK
 ---

DocGen/Documentation/HowTos/UsingWLT/BeforeGettingStarted.md

@@ -4,6 +4,7 @@ description: A few notes on WLT to consider before diving in.
 author: fast-slow-still
 ms.author: mafinc
 ms.date: 10/06/2021
+ms.prod: mixed-reality
 ms.localizationpriority: high
 keywords: Unity, HoloLens, HoloLens 2, Augmented Reality, Mixed Reality, ARCore, ARKit, development, MRTK
 ---
@@ -22,21 +23,31 @@ WLT has been carefully structured to handle the vast majority of usage cases wit
 
 ## Customizing behavior through code
 
-There are two cases where you might want to do additional coding against the WLT APIs.
+There are a small number of cases where you might want to do additional coding against the WLT APIs.
 
 First, you might want to customize your customers' experiences, especially in extraordinary circumstances, such as loss of tracking. Some such bespoke behavior is described in the [Handling exceptional conditions](LossOfTracking.md) section.
 
-The other case is where additional input is required from your application in order to perform a service for you. For example, in order to [align your coordinate system with physical world features](AlignMyCoordinates.md) in a desired way, you must give an indication of how you want the coordinate system aligned. This additional input comes in the form of pairs of virtual and tracking space poses.
+Secondly, you might want to do your WLT setup at runtime. Any configuration of WLT which can be done in the Unity Inspector can be done by script calls. Likewise, any WLT object or component that can be added to the scene and deployed at build time, can instead be added to the scene at runtime from script.
+
+The final case is where additional input is required from your application in order to perform a service for you. For example, in order to [align your coordinate system with physical world features](AlignMyCoordinates.md) in a desired way, you must give an indication of how you want the coordinate system aligned. This additional input comes in the form of pairs of virtual and tracking space poses.
 
 ## Start off easy
 
 WLT strives to maintain this pattern throughout. To get the most commonly desired functionality requires no coding and minimal setup. Default behavior is implemented as available components. Customizing the default behavior requires only enough code to override the provided behavior with the behavior you want. Additional features require only enough interaction with your application to indicate your intentions.
 
 There is a lot of API surface in WLT. Those are growth opportunities for farther down the road, so that WLT never boxes you in. But start off simple. You may find WLT does everything you require from it without a line of code.
 
+First, read and understand this conceptual documentation. At appropriate places you will find links to the API documentation, as a reference for exact calling syntax. Direct links to the overall API documentation are included below.
+
 ## See also
 
 * [Most Basic Setup](JustWorldLock.md)
 * [Loss of Tracking](LossOfTracking.md)
 * [Across Sessions](PersistenceTricks.md)
 * [Pinning It Down](AlignMyCoordinates.md)
+
+## API Documentation
+
+* [WLT Core](xref:Microsoft.MixedReality.WorldLocking.Core)
+* [WLT Tools](xref:Microsoft.MixedReality.WorldLocking.Tools)
+* [WLT with ASA](xref:Microsoft.MixedReality.WorldLocking.ASA)